The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Hybrid powertrains typically include an internal combustion engine (ICE), one or more electric motors (EMs), and one or more torque generators that provide torque to a driveline to propel a vehicle. Hybrid powertrains types include a full hybrid powertrain, a strong hybrid powertrain, a mild hybrid powertrain, etc. In a full hybrid powertrain, an EM drives the drivetrain directly, without transferring torque through a component of the ICE. In a strong hybrid powertrain, one or more electric motors may be incorporated as part of a transmission system and be coupled between the ICE and the drivetrain. The electric motors may be used for transmission gear ratio selection, rotation assist, and braking of the ICE, regeneration, etc.
In a mild hybrid configuration the EM is coupled to the ICE through an accessory drive. Torque generated by the EM is transferred to the drivetrain through the ICE. An exemplary mild hybrid powertrain may include a belt alternator starter (BAS) system. In the BAS system, the EM is connected to the ICE via a belt and pulley configuration, which drives other accessory components, such as pumps and compressors.
Powertrain torque control typically includes two torque control domains: axle torque and propulsion torque. In a mild hybrid powertrain, the propulsion torque is the output torque at the crankshaft of the ICE, which includes the EM torque contribution.
During an auto start of the engine a control module of a hybrid powertrain spins up the engine using the electric motor. An auto start, for example, may occur when a vehicle is active (a key start or the like has already occurred) and not moving, such as when a vehicle operator lets off a brake pedal and/or depresses an accelerator pedal. A crankshaft of the engine is typically rotated at higher speeds during an auto start than during a conventional startup of an engine via a starter. During an auto start, surges in engine speed and/or output torque of the hybrid powertrain may be experienced due to the activation of the ICE.